Cryptology ePrint Archive: Report 2015/442

Individualizing Electrical Circuits of Cryptographic Devices as a Means to Hinder Tampering Attacks

Zoya Dyka, Thomas Basmer, Christian Wittke and Peter Langendoerfer

Abstract: Side channel and fault attacks take advantage from the fact that the behavior of crypto implementations can be observed and provides hints that simplify revealing keys. In a real word a lot of devices, that are identical to the target device, can be attacked before attacking the real target to increase the success of the attack. Their package can be opened and their electromagnetic radiation and structure can be analyzed. Another example of how to improve significantly the success rate of attacks is the measurement of the difference of the side channel leakage of two identical devices, one of these devices being the target, using the Wheatstone bridge measurement setup. Here we propose to individualize the electrical circuit of cryptographic devices in order to prevent attacks that use identical devices: attacks, that analyze the structure of devices identical to the target device in a preparation phase; usual side channel attacks, that use always the same target device for collecting many traces, and attacks that use two identical devices at the same time for measuring the difference of side-channel leakages. The proposed individualization can prevent such attacks because the power consumption and the electromagnetic radiation of devices with individualized electrical circuit are individualized while providing the same functionality. We implemented three individualized ECC designs that provide exactly the same cryptographic function on a Spartan-6 FPGA. These designs differ from each other in a single block only, i.e. in the field multiplier. The visualization of the routed design and measurement results show clear differences in the topology, in the resources consumed as well as in the power and electromagnetic traces. We show that the influence of the individualized designs on the power traces is comparable with the influence of inputs. These facts show that individualizing of electrical circuits of cryptographic devices can be exploited as a protection mechanism. We envision that this type of protection mechanism is relevant if an attacker has a physical access to the cryptographic devices, e.g. for wireless sensor networks from which devices can easily be stolen for further analysis in the lab.

Category / Keywords: implementation / field multiplication, individualizing electrical circuit of multiplier, power traces, electromagnetic traces, countermeasures against side-channel attacks.

Date: received 8 May 2015

Contact author: dyka at ihp-microelectronics com

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Version: 20150509:152126 (All versions of this report)

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